Deformable well screen

ABSTRACT

A deformable well screen for preventing migration of solid particles into a hydrocarbon production well is disclosed, the screen including at least one substantially tubular filter layer of which the sieve opening size remains fairly constant during or after expansion and/or other formation of the screen. Optionally the screen also includes a series of circumferentially scaled filter segments that are arranged around an expandable slotted tube, an expandable slotted tube of which the slots are filled with resin coated granules, an expandable slotted tube with micro-slots, an assembly of woven metal wire screens that are sintered together and/or a synthetic geotextile fabric.

FIELD OF THE INVENTION

The invention relates to a well screen for preventing migration of solidparticles, such as sand and other formation minerals, gravel and/orproppant, into a hydrocarbon production well. More particularly, theinvention relates to a well screen comprising at least one substantiallytubular filter layer of which the sieve opening size is tailored to thesize of particles that are to be blocked by the screen.

BACKGROUND TO THE INVENTION

UK patent specification 2,115,040 discloses a wellbore screen. Thisscreen may include outer and/or inner protective layers which areco-axial to the filter layer and which have a much larger sieve openingsize than the filter layer or layers.

A problem encountered with the screen of UK patent specification '040 isthat woven metal wire and other filter sheets are fragile and can beeasily squeezed and damaged during installation and use. Only a minordeformation of the filter sheet may already result in variation of thesieve opening which may hamper a proper performance of the screen.

Furthermore sand screens of the known type are typically made in a flator tubular shape and are designed to remain in their original shapewithout substantial deformation during and/or after installation.However, in boreholes with an irregular surface and/or sharp bends thisrequires the use of a screen with a much smaller diameter than that ofthe wellbore. Such use of a small diameter screen will result in highfluid flowrates through the sieve openings of the screen, strong wear ofthe screen and an increased risk of plugging of the screen and ofcollapse of the borehole.

It is an object of the invention to alleviate the problems.

SUMMARY OF THE INVENTION

The screen according to the invention thereto is deformable such that itcan be expanded, bent, compressed and/or fluidized during installationof the screen within a wellbore and that any variation of the sieveopening size of the screen as a result of such deformation remainswithin predetermined limits.

Preferably the screen is expandable downhole to such a size that it, ora surrounding protective layer, can be set at least partly against thesurrounding formation. At locations, such as washouts and doglegs, wherethe borehole wall is so irregular that still a gap would remain aroundthe expanded screen a resin impregnated gravel could be placed in thegap to ensure a continuous mechanical contact between the screen andformation.

Optionally the screen according to the invention is arranged around anexpandable slotted tube which induces the internal diameter of thescreen to be increased during installation of the screen and tubeassembly in a wellbore while the variation in sieve opening size of eachfilter layer of the screen as a result of such expansion of the screenis less than fifty per cent.

A suitable expandable slotted tube for use with the screen is disclosedin the specification of international patent application PCT/EP93/101460.

In a preferred embodiment the screen according to the inventioncomprises a series of scaled filter sheets which are arranged around anexpandable slotted carrier tube and which, when seen in acircumferential direction, are connected at one edge to said tube and atanother edge at least partly overlap an adjacent filter sheet.Optionally, the scaled filter sheets are made of a flexible permeablematerial which is selected from the group of a perforated metal plate, ametal plate comprising an array of substantially tangential slots,sintered woven metal wires and a synthetic fabric.

In another preferred embodiment the screen according to the inventioncomprises an expandable slotted tube of which the slots and any gapsbetween the tube and borehole wall have been filled in situ withgranules that are bonded to each other and to the rims of the slots by abonding agent such that pore openings of a selected size remain betweenthe granules.

In the above embodiments the slotted tube can be expanded to a diameterwhich may be 50% larger than the diameter of the unexpanded tube. Thesieve opening size of the screen remains substantially unaffected bysuch large expansion although the scaled filter sheets may be stretchedin a circumferential direction as a result of frictional forces anddeformed slightly by the axial contraction of the slotted carrier tubeduring the expansion process.

In a suitable embodiment the screen according to the invention comprises

at least one tubular filter layer which is made of a woven metal wirescreen; and

an outer protective layer which co-axially surrounds the filter layer orlayers and an inner protective layer which is fitted co-axially withinthe protective layer or layers, which protective layers comprise each awoven metal wire screen having a larger sieve opening size and wirethickness than at least one of the filter layers, and wherein the filterand protective layers are sintered together.

A principal advantage of sintering the various layers of woven metalwire screen together is that it produces a screen having a sectionmodulus which is greater than the sum of section moduli of theindividual layers. This results in a robust screen of which the sievesize does not change significantly during or after deformation whichmake the screen coilable around a drum and installable into a well byreeling the screen from the drum.

Optionally at least one filter layer comprises wires which are orientedin a substantially helical weaving pattern relative to a central axis ofthe tubular screen.

It has been found that if said pitch angle is approximately 45° thenlocal elongation and/or shortening caused by expansion, compressionand/or bending of the tubular screen then a square mesh sieve will bedeformed to a diamond pattern, and the sieve opening will only changeslightly and by a predictable amount.

A tubular screen having a helical weaving pattern can be convenientlymanufactured from sheets or strips having the wires substantiallyparallel and normal to the edges, by forming those sheets or strips intoa helically wound tubular shape having abutting edges, and welding theabutting edges together, as is done for example for helically weldedmetal tubes.

It is observed that SU patent specification 1,066,628 discloses that ascreen can be made by scrolling six layers of metal filtration clotharound a perforated metal tube and then sintering the pack. However, inthe known screen the various layers are made of the same cloth. Thiswill generally cause the wires of adjacent layers to partly block thesieve openings of adjacent layers which will reduce the effective sieveopening in a rather irregular and unpredictable way.

Other screens are disclosed in U.S. Pat. Nos. 2,858,894 and 3,087,560and in a sales brochure of Haver and Boecker concerning screens soldunder the trademark "POROPLATE".

In an alternative embodiment of the screen according to the inventionthe screen comprises at least one filter layer which is substantiallymade of a fabric, such as a needlefelt. Suitably the needlefeltcomprises a material selected from the group of steel wires andsynthetic fibers. Optionally the synthetic fibers are selected from thegroup of aramid fibers and "CARILON" polymer fibers which have a highchemical resistance. "CARILON" polymer is a linear alternating copolymerof carbon monoxide and one or more olefinically unsaturated compounds.European patent specifications Nos. 360,358 and 310,171 disclose methodsfor the manufacture of fibers of this polymer by gel and melt spinning,respectively. Preferably the filter layer comprises an elongate fabricstrip which is wound in an overlapping helical pattern into a tubularshape, whereby adjacent windings have an overlap of between 10% and 90%,preferably about 50%.

It is observed that international patent application PCT/EP/01460discloses that two co-axial slotted liners may be placed within thewellbore such that after expansion the slots are not in line in radialdirection. This non-overlapping arrangement aims to induce fluids totraverse through the liners via a zig-zag path thereby preventing sandfrom entering the borehole. The liners used in this prior art referencecomprised axial slots having a length of at least 25 mm and a width ofat least 0.7 mm.

Surprisingly it was found that instead of using the interaction betweennon-overlapping relatively large slots of co-axial liners to preventinflow of sand a suitable screen may be created by using a singleexpandable tube having micro-slots.

Therefore, in yet another alternative embodiment of the screen accordingto the invention the screen comprises an expandable tubular body withmicro-slots that are arranged in a staggered and overlapping patternwhich slots substantially have a length less than 10 mm before expansionof the tubular body.

Preferably the micro-slots substantially have before expansion of thetubular body a length less than 5 mm and a width less than 0.3 mm.

A principal advantage of the use of a single expandable sand-screen withmicro-slots over the use of co-axial liners with non-overlappingrelatively large slots is that it generates a screen with a more regularsubstantially diamond-shaped sieve opening size after expansion.

Suitably the expandable tubular body with micro-slots is made of nickeland has a wall thickness which is less than 1 mm. In order to protectsuch a fragile body from damage during and after installation it ispreferred to arrange the body co-axially between two conventionalexpandable slotted liners having larger slots and a larger wallthickness than the body. Suitably these protective liners are made ofsteel and comprise slots having a length of at least 15 mm and a widthof at least 2 mm.

U.S. Pat. No. 1,135,809 discloses a well screen with staggered axialslots. The screen according to this prior art reference, however, isinstalled downhole without being subject to any significant expansion orother deformation, so that the slots remain in their original elongateshape.

The invention also relates to a method for installing a tubular wellscreen in a hydrocarbon production well, the method comprising arrangingthe screen around an expandable slotted tube, lowering the screen andtube assembly into the well, inducing the tube to expand therebyincreasing the internal diameter of the screen to be increased with atleast five per cent while any variation of the sieve opening size ofeach filter layer of the screen is less than fifty per cent.

Optionally the screen and tube assembly is wound around a drum andreeled from said drum into the well during installation.

In an alternative embodiment the method according to the inventioncomprises lowering an expandable slotted tube into the well, inducingthe tube to expand, injecting granules coated with a bonding agent intothe expanded tube and wiping the granules at least partly away from saidinterior into the expanded slots of the tube and any gaps that may bepresent between the expanded tube and the borehole wall, and allowingthe bonding agent to cure. In this way a permeable matrix of bondedsolid particles is formed which substantially fills the expanded slotsand any gaps between the expanded tube and the borehole wall.

The coated granules may consist of resin coated granules having adiameter between 1 and 5 mm which are injected via injection partslocated behind the expansion cone and a wiper set may be trailed behindthe cone in order to wipe the granules from the interior of the expandedtube into the slots and any gaps surrounding the tube.

These and other features, objects and advantages of the method andscreen according to the invention will become apparent from theaccompanying claims, abstract and the following detailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a cross-sectional view of a segmented screen which islowered into a well between two unexpanded slotted tubes;

FIG. 2 shows a cross-sectional view of the screen and tube assembly ofFIG. 1 after expansion of the assembly;

FIG. 3 is a side view of a section of one of the filter sheets of thesegmented screen of FIG. 1 and 2 shown at an enlarged scale;

FIG. 4 is a side view of a section of the unexpanded slotted carrier andprotective tube of FIG. 1 shown at an enlarged scale;

FIG. 5 is a side view of a section of the expanded carrier andprotective tube of FIG. 2 shown at an enlarged scale; and

FIG. 6 is a schematic longitudinal sectional view of an expandingslotted tube where resin coated granules are wiped into the slots toform, after curing of the resin, a sandscreen.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 and 2 there is shown a borehole 1 passingthrough an underground hydrocarbon bearing formation 2.

An assembly of an expandable slotted carrier tube 3, a well screencomprising four scaled perforated filter sheets 4 and an expandableslotted protective tube 5 has been lowered into the borehole 1.

Each filter sheet 4 is connected near one edge to the carrier tube 3 bya lug 6 such that at an opposite edge it overlaps an adjacent sheet 4.

The lugs 6 permit the filter sheets 4 to move axially with respect tothe carrier tube 3 and in that way to enable the axial contraction ofthe carrier tube 3 as a result of tangential expansion to be compensatedfor by axial sliding of the filter sheets 4 over the carrier tube.

In FIG. 1 the assembly is in an unexpanded form so that the slots 7 ofthe two slotted tubes 3 and 5 have an elongate longitudinal shape and aconstant width, when seen in circumferential direction as shown in FIG.4, the filter sheets 4 in a longitudinal direction the sheets may alsobe wrapped helically around the carrier tube 3 at such pitch angle thatthe sheet will contract during the expansion in longitudinal directionin substantially the same way as the slotted tube 3.

During the expansion process adjacent filter sheets 4 will sliderelative to each other and the sheets 4 will also slide relative to theinner wall of the protective tube 5.

In the embodiment shown the sheets 4 are made of a perforated nickelfoil which is a low friction material.

In order to further reduce friction during expansion the filter sheets 4may comprise substantially tangential slots instead of the circularperforations shown in FIG. 3. The width of such tangential slots willnot change significantly during expansion of the assembly within theborehole 1.

Instead of using a nickel foil for the filter sheets 4 these sheets mayalso be made of another material, such as a sintered woven wire mesh anda synthetic fabric which are described in more detail elsewhere in thisspecification.

Instead of using a slotted steel protective tube 5 around the filtersheets 4 any other expandable and permeable protective tubular body maybe used, such as a knitted geotextile sock or a scrolled perforatedmetal sheet. Instead of using a plurality of filter sheets which eachonly partly surround the carrier tube 3 also a single scrolled filtersheet may be used which is not secured. As an alternative to using lugs6 for connecting the filter sheets 4 to the carrier tube 3, the sheets 4may be spot welded or connected by other mechanical fasteners to thecarrier tube.

In FIG. 2 the assembly is shown in an expanded form so that the slots 7of the slotted tubes 3 and 5 have a diamond shape as can be seen in FIG.5. Expansion of the assembly may be accomplished by moving an expansioncone through the steel carrier tube 3 as described in internationalpatent application PCT/EP93/01460, whereby the expansion of the carriertube also induces the outer tube 5 to expand until it substantiallyengages the borehole wall.

During the expansion process overlap between adjacent filter sheets 4 isreduced, but the circumferential length of the scaled sheets 4 isselected sufficiently large that still at least some overlap remainsafter the expansion.

As illustrated in FIG. 3 the filter sheets 4 consist of perforatedplates and the width of the perforations remains substantially the sameduring and after the expansion process. However, the carrier tube 3 willcontract slightly in longitudinal direction as a result of the expansionprocess. Therefore it is preferred to arrange the lugs 6 within slotswhich permit the lugs 6 to slide in longitudinal direction relative tothe carrier tube 3. However instead of using lugs the front edges of thefilter sheets 4 may also be secured to the carrier tube 3 by spotwelding. In such case this may result in some longitudinal compaction ofthe front edges of the filter sheets during the expansion process ifthese front edges have a longitudinal orientation. However,alternatively the front edges of the filter sheets 4 may have a helicalorientation relative to the carrier tube 3. In such case one or morefilter sheets 4 may be wrapped helically around the carrier tube 3 suchthat opposite edges of the filter sheet overlap each other both in theunexpanded and the expanded position of the carrier tube 3.

FIG. 6 shows an embodiment of the screen according to the inventionwhere a screen is formed in situ within the borehole. An expandableslotted steel tube 10 is expanded against the borehole wall 11 bypulling an expansion cone 12 upwardly through the tube 10.

The cone 12 is suspended at the lower end of a coiled tubing 13 viawhich resin coated granules 14 are injected which pass via injectionports 15 just below the cone 12 into the interior of the expanding tube10. A set of two disk-shaped wipers 16 is trailed behind the cone by arod 17 which press the granules 14 out of the interior of the expandedtube 10 into the expanded slots 18 and any gaps 19 that may be presentbetween the borehole wall 11 and the expanded tube 10. After curing ofthe resin the granules are bonded to a permeable matrix of granuleswhich fills the expanded slots 18 and which is also bonded to the rimsof these slots 18. The diameter of the granules 14 is selected such thatthe pores between the granules 14 form sieve openings of a size suitableto prevent ingress of sandgrains into the well. For most sandgrain sizesa suitable granule size is between 0.5 and 5 mm.

Another deformable well screen was constructed from seven layers of wiremesh woven in a plain rectangular weave pattern with respectively thefollowing sieve opening sizes: 5000/950/162/625/325/950/5000 μm.

These layers were sintered together in a vacuum to form a plate, whichwas then rolled into the form of a tube and seam welded.

The layers consisted of sheets of woven wire mesh of 350 mm long and 170mm wide which were sintered together in a vacuum furnace between twoplates of cordierite ceramic. These plates were pressed together by a 9kg weight. The material was sintered for four hours at 1260° C. and apressure of 10⁻⁴ Pa. The material was allowed to cool in the furnaceunder vacuum.

After the sintering procedure the stack of layers was about 9 mm thick.It was then rolled in a rolling mill to a thickness of 5 mm in one passand sintered for a further four hours under the same conditions.

The sintered plate was subsequently cut to a length of 310 mm and placedin a 3-roll bending machine with the 170 mm edge parallel to the rollaxis and rolled to make a tube of about 100 mm diameter and 170 mm long.

The seam was then brazed. However, if desired, it would have beenpossible to weld the seam. In the thus created tubular screen the layerswith the sieve opening sizes of 162 and 325 μm acted principally as thefilter layers whereas the other layers, viz those with sieve openingsizes of 625, 950 and 5000 μm acted essentially as protective layers.The filter layer with the finest sieve opening size, i.e. 162 μm,surrounded the filter layer with the coarser sieve opening size, i.e.325 μm, to reduce sand accumulation within the screen.

The following tests were carried out with sintered woven wire sieveplates according to the invention.

A short length of a tubular sieve plate was axially compressed betweenplatens in a press to reduce its length by 10%. The tube walls showedincipient buckles. No obvious changes in sieve opening size were foundin a visual inspection. The length changes in the finest meshaccommodated by bulging outwards between the wires of the coarser mesh,with apparent retention of weave pattern and sieve opening dimensions.

Furthermore a disc of sintered mesh was placed in a 0.5 m long cell, 50mm diameter, containing 1500 g sand from a hydrocarbon fluid productionwell in Uiterburen, the Netherlands. Air at 100 bar was flowed throughthe sand bed and the screen for a week at a nominal velocity through thescreen of 5 m/s. The pressure drop over sand bed and screen remainedconstant at 3 bar.

The weight of the sand recovered from the cell after the test was 9 gless.

It was concluded from this test that the screen stabilized the sandsufficiently to prevent significant migration of the fine sand. Furtherthe screen was not plugged to the extent that a significant increase inpressure drop resulted.

It was also concluded that the combination of protective layers having acoarse mesh and made from thick wire with filter layers with fine meshthat are sintered together creates a robust structure with a fine sievesize. Sintering the various layers together produces a screen having asection modulus which is greater than the sum of section moduli of theindividual layers.

The weaving patterns and wire gauges in the various layers can beselected to give the desired combination of strength and compliance inradial, circumferential and longitudinal directions so that the screencan be made as a self supporting tube which can be reeled from a druminto the well and then expanded downhole.

If the predominant weaving pattern has its warp axis parallel to thetube axis and the warp threads are bent over and under the weft threads,while the latter are relatively undistorted (as for example in reversedplain Dutch weave or reversed Dutch twill) then the yield strain inlongitudinal bending will be relatively high but at relatively lowstress, and the tube can be easily bent; while if the weft threads arebent and the warp threads straight (plain Dutch weave or Dutch twill)the tube can be more easily expanded or reduced in diameter. If the warpand weft threads are at an angle of 45° to the tube axis (as inhelically welded tube) then a square mesh weave will be deformed to adiamond pattern as a result of any deformation causing length ordiameter changes, and the sieve aperture will only change slightly andby a predictable amount. If two layers of the fine mesh are separated bycoarse mesh, sand eroding the first layer will accumulate in the spacebetween the two layers and offer some protection against erosion to thesecond layer, not only by forming a barrier but also by locally reducingthe permeability and hence the flow. If the outermost fine mesh has asmaller sieve opening size than the next fine layer, then any materialwhich passes through the outer fine layer may also pass throughsubsequent fine layers, reducing the tendency of the screen to internalplugging. Preferably the sieve opening size of the outermost filterlayer is at least two times smaller than any of the other filter andprotective layers.

Yet another deformable well screen was made of a non-woven needlefeltconsisting of aramid fibers which is marketed by the company Duflotunder the trademark "KEVLAR" EA 205.

The needlefelt was 4 mm thick, had a weight of 400 g/m² and wasmanufactured by needle punching.

A needlefelt sheet was brought into a tubular shape and the engagingends of the sheet were stitched together. The thus formed tubular screenwas then arranged around an expandable slotted tube which initially hadan internal diameter of 38 mm. The tube was subsequently expanded to aninternal diameter of 80 mm. Before and after the expansion the wallthickness of the tube was 5 mm. The force required to pull a conethrough the tube in order to expand the tube and screen assembly was 30KN. This is 6 KN more than the force required for expansion of theexpandable slotted tube alone.

The expansion of the screen did not cause any damage to the needlefeltor to the stitches. The thickness of the needlefelt was reduced by37.5%.

The expanded tube and screen assembly had a length of 285 mm and wasplaced in a tubular container with a 30 mm thick annular layer of sandaround the screen. The sand was 0-0.1 mm sand from a hydrocarbon well inPekela, the Netherlands. The sand had a permeability K=2.10 Darcy and aporosity n(p)=42.39%.

Water was pumped radially via six injection points through the annularsand pack and screen into the interior of the expanded tube and thencirculated back during a period of six hours.

During the test the fluid pressure inside the tube was about 2.6 bar andthe fluid pressure at the injection point was about 2.7 bar.

The water flux through the screen was 5 l/min. Throughout the test nosand was detected in the circulated water and the pressure drop acrossthe sand pack and screen remained constant at about 0.1 bar. From thetest it was concluded that the expansion of the screen had caused nosignificant effect on the performance of the screen as a sand filter andthat thus only minor variations in sieve opening size of the screen hadoccurred as a result of the expansion.

The test was repeated with a silt fraction of 15μ to 63μ, smeared ontothe screen, which yielded a similar favorable result.

Further the longevity of the needlefelt screen was tested by clamping itbetween steel plates with circular holes of various sizes. The steelplates were located such that the corresponding holes in the respectiveplates were co-axial. The plates with the needlefelt exposed at thelocation of the holes were then sandblasted for substantial periods.

No damage to the needlefelt screen was observed after the test for theholes smaller than 5 mm diameter.

It was concluded from the various tests that a needlefelt or othergeotextile fabric is suitable for use as a deformable sandscreen. It wasalso concluded that such a screen can be made and installed in a costeffective manner by arranging a tubular fabric layer between twoperforated co-axial pipes. Such an assembly of fabric layer and pipescan be reeled on a drum and transported to the well site, where theassembly is reeled from the drum into the well. The fabric layer mayconsist of an elongate strip which is wound helically around the innerperforated pipe such that adjacent windings of the strip at least partlyoverlap each other.

The above assembly is particularly attractive if a screen of substantiallength is to be installed in a compacting reservoir.

Alternatively a tubular needlefelt or other fabric layer is arrangedbetween a pair of co-axial expandable slotted tubes. In such case thefabric may also consist of a strip which is wound helically around theinner expandable tube such that a substantial overlap exists betweenadjacent windings of the strip before expansion of the tubes.

The overlap is in such case selected sufficiently large that afterexpansion of the assembly at least some overlap remains between adjacentwindings of the fabric strip.

Reference is now made to yet another embodiment of the deformabletubular well screen according to the invention which is not illustrated.In this embodiment the screen comprises a tubular screen in which axialslots are present, which slots are regularly distributed in a staggeredpartly overlapping pattern over the surface of the screen. The testedscreen was made of a nickel tube which had before expansion an internaldiameter of about 145 mm and a wall thickness of 0.66 mm. The slots eachhad a length of about 3.5 mm and a width of 0.15 mm before expansion.The slots were pitched 5 per 24.5 mm longitudinally and 17 per 24.5 mmcircumferentially, the longitudinal axis of the slots being parallel tothe tube.

One millimeter thick steel protective expandable slotted tubes wereco-axially arranged within and around the screen. The protective tubeseach comprised slots having before expansion a length of about 20 mm anda width of about 2.2 mm. The slots in these protective tubes werepitched at 24 mm longitudinally and 4.2 mm circumferentially.

A 2 m long assembly of the nickel sand screen and steel protectivescreen was arranged within a steel casing having an internal diameter ofabout 160 mm and in which nine inspection holes having a diameter ofabout 30 mm were present.

The assembly was expanded against the inner wall of the casing bypulling a cone through the assembly. Visual examination of the assemblydemonstrated a tight fit between the assembly and casing and asubstantially uniform expansion of the protective tubes and the nickelsand screen. As a result of the expansion the slots of the nickel sandscreen had opened up to a diamond shape and the smallest width of theslots was between 0.3 and 0.4 mm. It was concluded that small variationsin the slot widths were due to slight variations in the exact amount ofexpansion and that these variations were within acceptable limits.

A flow test was carried out during which tap water was allowed to flowvia three inspection holes through the screen at rates of between 8 and10 liters per minute. During the test the pressure drop across thescreen remained between 0.1 and 0.2 bar.

A ten meter long version of this screen was installed and tested in anoil well in Oman. The production data show that not only does the screencontrol sand production without the need for gravel packing but alsothat the well's productivity is unimpaired compared to its productivitybefore installation of the screen. The screen also showed no signs ofplugging over a sustained period of production.

We claim:
 1. A deformable well screen for preventing migration of solidparticles into a hydrocarbon production well, which screen comprises:atleast one substantially tubular filter layer having a sieve opening sizewhich is tailored to the size of particles that are to be blocked by thescreen, wherein the filter layer is deformable such that it can beexpanded, bent, and/or compressed during installation of the screen in awellbore and that any variation of the sieve opening size of each filterlayer as a result of such deformation remains within predeterminedlimits wherein the filter layer comprises a series of scaled filtersheets which are arranged around an expandable slotted carrier tube andwhich, when seen in a circumferential direction, are connected at oneedge to said tube and at another edge at least partly overlap anadjacent filter sheet.
 2. The well screen of claim 1, wherein the wellscreen is coilable around a drum and installable into a well by reelingthe screen from the drum.
 3. The well screen of claim 1 wherein thefilter sheets are connected to said carrier tube by a series of lugsthat are hooked onto the carrier tube and wherein an expandable slottedprotective tube surrounds the filter layer.
 4. The well screen of claim1 wherein the filter sheets are made of a flexible permeable materialwhich is selected from the group consisting of a perforated metal plate,a metal plate comprising an array of substantially tangential slots, asintered woven metal wire and a synthetic fabric.
 5. The well screen ofclaim 1 wherein the deformable tubular filter layer which is made of awoven metal wire screen; and the screen further comprises;an outerprotective layer which co-axially surrounds the filter layer or layersand an inner protective layer which is fitted co-axially within theprotective layer or layers, which protective layers comprise each awoven metal wire screen having a larger sieve opening size and wirethickness than at least one of the filter layers, and wherein the filterand protective layers are sintered together.
 6. The well screen of claim5 wherein at least one filter layer comprises wires which are orientedin a substantially helical weaving pattern relative to a central axis ofsaid layer.
 7. The well screen of claim 6 wherein a helix defined by thehelical weaving pattern is oriented at a pitch angle between 40° and 50°relative to said central axis.
 8. The well screen of claim 6 wherein thescreen comprises filter sheets that are brought into a helical shape andwelded together is a substantially non-overlapping helical pattern. 9.The well screen of claim 5 comprising an inner and an outer filter layerwhich are co-axial to each other and separated by an intermediate layerwhich is made of a woven wire having a larger sieve opening than thefilter layers and which is sintered to the filter layers, and whereinthe outer filter layer has a smaller sieve opening than the inner filterlayer.
 10. The well screen of claim 9 wherein a pair of outer protectivelayers surrounds the outer filter layer and a pair of inner protectivelayers is fitted within the inner filter layer and wherein the outermostouter protective layer and the innermost inner protective layer have alarger sieve opening size than the other layers.
 11. The well screen ofclaim 1 wherein the screen comprises at least one filter layer which issubstantially made of a fabric.
 12. The well screen of claim 11 whereinthe filter layer comprises an elongate fabric strip which is wound in anoverlapping helical pattern into a substantially tubular shape.
 13. Thewell screen of claim 1 wherein the screen comprises an expandabletubular body with longitudinal micro-slots that are arranged in astaggered and overlapping pattern, which micro-slots substantially havebefore expansion of the tubular body a length less than 10 mm.
 14. Thescreen of claim 13 wherein the tubular body is made of nickel and themicro-slots substantially have a length less than 5 mm and a width lessthan 0.3 mm.
 15. A method of installing a deformable well screen in ahydrocarbon production well, the method comprising the stepsof:arranging the screen around an expandable slotted tube; lowering thescreen and tube assembly into the well; and expanding the tube andthereby increasing the internal diameter of the screen to be increasedwith at least five per cent while any variation of the sieve openingsize of each filter layer of the screen is less than fifty per cent. 16.The method of claim 15 wherein the screen and tube assembly is woundaround a drum and reeled from said drum into the well duringinstallation.